Fuel cell operation system and valve open amount calculation method in the fuel cell operation system

Abstract

FC current control in a fuel cell operation system can be roughly divided into two parts. The first part executes a total air feed amount calculation step, an FC air amount calculation step, and a bypass air amount calculation step. These steps are executed by using a stoichiometry map and a pumping hydrogen amount map. The second part calculates a control valve open amount instruction value and a bypass valve open amount instruction value according to the calculated FC air amount and the bypass air amount. Here, a control valve open amount map and the like are used. When generated power is output from the fuel cell stack by these instruction values, the actual FC current value is compared to the FC current instruction value and the control valve open amount is corrected according to a difference between them.

1. A fuel cell operation system, comprising:
 a fuel cell; 
 a fuel gas supply device that supplies a fuel gas to an anode side of the fuel cell; 
 an oxidizing gas supply device that supplies an oxidizing gas to a cathode side of the fuel cell; 
 an inlet side flow path that connects between the oxidizing gas supply device and a cathode side gas inlet of the fuel cell; 
 an outlet side flow path connected from a cathode side gas outlet of the fuel cell to an exhaust side; 
 a bypass flow path that connects between the inlet side flow path and the outlet side flow path and is arranged in parallel with the fuel cell; 
 a control valve provided in at least one of the inlet side flow path and the outlet side flow path to adjust a gas flow rate at the cathode side; 
 a bypass valve provided in the bypass flow path to adjust a gas flow rate in the bypass flow path; and 
 a control unit that controls operation of the fuel cell, 
 wherein the control unit is programmed to: 
 obtain a bypass valve differential pressure which is a differential pressure between upstream and downstream of the bypass valve by applying an open amount of the bypass valve and the gas flow rate in the bypass flow path to pre-obtained flow characteristics of the bypass valve; and 
 obtain an open amount of the control valve by applying the bypass valve differential pressure and the cathode side gas flow rate to both characteristics of pre-obtained cathode side flow characteristics of the fuel cell and flow characteristics of the control valve. 
 
     
     
       2. The fuel cell operation system according to  claim 1 , wherein:
 the fuel gas is hydrogen; and 
 the control unit further comprises: 
 an obtaining part to obtain a pumping hydrogen amount for the cathode side within the fuel cell based on an output power required of the fuel cell; 
 an obtaining part to obtain a gas flow rate at which gas is supplied to the cathode side gas inlet based on the output power required of the fuel cell; and 
 an obtaining part to obtain a gas flow rate at which gas is passed through the bypass flow path based on the obtained pumping hydrogen amount. 
 
     
     
       3. The fuel cell operation system according to  claim 2 , wherein:
 the control unit further comprises an obtaining part to obtain an unreacted hydrogen flow rate which is an unreacted fuel gas flow rate at the anode side; and 
 the obtaining part to obtain a gas flow rate at which gas is passed through the bypass flow path comprises obtaining a gas flow rate at which gas is passed through the bypass flow path based on the pumping hydrogen amount and the unreacted hydrogen gas flow rate at the anode side. 
 
     
     
       4. The fuel cell operation system according to  claim 2 , wherein:
 the control unit further comprises a correcting part to correct the open amount of the control valve based on a difference between an actual generated power output from the fuel cell which is operated under the obtained open amount of the control valve and the output power required of the fuel cell.